This invention relates to a sheet aligning device having a pair of side walls located on opposite sides of a multiplicity of successively fed sheets at least one of which is movable in reciprocatory movement toward and away from the sheets widthwise thereof to bring the sheets into alignment with each other in a direction perpendicular to the direction in which the sheets are fed.
Copying apparatus, printers or their peripheral devices (such as automatic document feed devices, sheet folding machines, punching machines, sheet binding machines, etc.) usually comprise sheet aligning devices of the type described for aligning copies, printed sheets, documents and other sheets. In copying apparatus for copying opposite sides of a document, for example, copy sheets each having an image of an original formed on one side surface are placed on a tray of an intermediate sheet feeding device and then fed again therefrom. In this case, the copy sheets fed to the tray should be brought into alignment with each other widthwise thereof in a predetermined position.
The reason why it is necessary to bring the sheets into alignment with each other by a sheet aligning device is because sheets fed to a tray, for example, might be displaced, when they are delivered, from a predetermined position on which they are to be stacked widthwise of each other (a direction perpendicular to the direction in which the sheets are fed) with the superposed sheets either being aligned lengthwise thereof or skewed with respect to the direction in which they are fed. The widthwise displacement of the sheets may vary in magnitude depending on the material of the sheets, their surface smoothness, their size or ambient conditions (humidity, temperature). Some type of sheets might be displaced greatly while other type of sheets might not show displacement at all. The latter type of sheets can be readily handled by a sheet aligning device. However, difficulties are experienced in bringing the former type of sheets into alignment with each other.
In sheet aligning devices of the prior art, no consideration has been paid to the condition of the sheets before they are handled by the device and it has been customary to move the side walls at a uniform speed, frequency and stroke in reciprocatory movement in an attempt to align the sheets with each other. Thus, the devices of the prior art have suffered the disadvantage that they are unable to satisfactorily accomplish the object of aligning the sheets when the magnitudes of their displacements are great. To obviate this disadvantage, one only has to move the side walls in reciprocatory movement each time a sheet is fed so that the side walls will strike one sheet several times, to reduce the speed of movement of the side walls to facilitate alignment of the sheets or to increase the stroke of the side walls so that the side walls will shift the sheets with a greater force, so as to thereby bring the sheets into alignment with each other even if the magnitudes of their displacements are great. It will be possible to satisfactorily align the sheets if the operation is performed over a prolonged period of time by increasing the frequency of reciprocatory movement of the side walls or reducing the speed thereof. However, as noted hereinabove, the magnitudes of displacements of sheets may vary depending on the material of the sheets and other factors, and not all the types of sheets are displaced from each other a large magnitude. Thus, if the sheet aligning operation is performed over a prolonged period of time by increasing the frequency of reciprocatory movements of the side walls, a period of time longer than is necessary would have to be spent in handling sheets which show little or no displacements. A loss of time would be enormous when a multiplicity of sheets are handled if the frequency of movements of the side walls is increased or the time required for handling each sheet is prolonged. Also, as subsequently to be described in detail, the intervals at which the sheets are successively fed should be increased. An apparatus, such as a printer or a copying apparatus, equipped with this type of sheet aligning device of the prior art would suffer the disadvantage that its peripheral equipment is very low in efficiency.